Epitope specificity of murine and human bactericidal antibodies against PorA P1.7,16 induced with experimental meningococcal group B vaccines

Synthetic peptides derived from the predicted loops 1 and 4 of meningococcal PorA, sero-subtype P1.7,16, were used to study the epitope specificity of murine and human PorA P1.7,16 bactericidal antibodies. The predicted loops 1 and 4 are surface exposed and carry in their apices the sero-subtype epitopes P1.7 (loop 1) or P1.16 (loop 4), respectively. Peptides were synthesized as mono- and multimeric peptides. Murine monoclonal and polyclonal antibodies were induced with meningococcal whole cell preparations. Polyclonal antibodies were evoked in volunteers after one immunization with 50 μg or 100 μg protein of a hexavalent meningococcal PorA vesicle vaccine. The induction of PorA antibodies was determined in ELISA using purified PorA P1.7,16. The epitope specificity of anti-PorA antibodies for both murine and human antibodies could be demonstrated by direct peptide ELISA using overlapping multimeric peptides almost spanning the entire loops 1 or 4 of the protein. The capacity of peptides to inhibit the bactericidal activity of murine and human antibodies was investigated using meningococcal strain H44/76 (B:15:P1.7,16) as a target strain. Bactericidal activities could be inhibited with both monomeric and multimeric peptides derived from epitopes P1.7 and P1.16.     

Antigenic drift of non-encapsulated Haemophilus influenzae major outer membrane protein P2 in patients with chronic bronchitis is caused by point mutations

The sequence of the gene encoding major outer membrane protein (MOMP) P2 of antigenic variants of non-encapsulated Haemophilus influenzae isolated from persistently infected chronic bronchitis patients was analysed. Antigenic drift was shown to result from single base changes in the P2 gene, all generating amino acid changes in the surface-exposed loops of MOMP P2, predominantly in loop 6. Similar single base changes were observed in H. influenzae persistently present in a subcutaneous cage implanted in rabbits, as well as in a spontaneous H. influenzae mutant that had survived MOMP P2 specific monoclonal-antibody-dependent bactericidal killing in vitro. We hypothesize that accumulation of point mutations under the selection pressure of immunity is a mechanism of antigenic drift of a surface-exposed protein during persistent H. influenzae infection     

Bacterial Meningitis in Brazil: Baseline Epidemiologic Assessment of the Decade Prior to the Introduction of Pneumococcal and Meningococcal Vaccines

Background

Bacterial meningitis is associated with significant burden in Brazil. In 2010, both 10-valent pneumococcal conjugate vaccine and meningococcal capsular group C conjugate vaccine were introduced into the routine vaccination schedule. Haemophilus influenzae type b vaccine was previously introduced in 1999. This study presents trends in demographics, microbiological characteristics and seasonality patterns of bacterial meningitis cases in Brazil from 2000 to 2010.

Methods and Findings

All meningitis cases confirmed by clinical and/or laboratory criteria notified to the national information system for notifiable diseases between 2000 and 2010 were analyzed. Proportions of bacterial meningitis cases by demographic characteristics, criteria used for confirmation and etiology were calculated. We estimated disease rates per 100,000 population and trends for the study period, with emphasis on H. influenzae, N. meningitidis and S. pneumoniae cases. In the decade, 341,805 cases of meningitis were notified in Brazil. Of the 251,853 cases with defined etiology, 110,264 (43.8%) were due to bacterial meningitis (excluding tuberculosis). Of these, 34,997 (31.7%) were due to meningococcal disease. The incidence of bacterial meningitis significantly decreased from 3.1/100,000 population in 2000–2002 to 2.14/100,000 in 2009–2010 (p<0.01). Among cases of meningococcal disease, the proportion of those associated with group C increased from 41% in 2007 to 61.7% in 2010, while the proportion of group B disease progressively declined. Throughout the study period, an increased number of cases occurred during winter.

Conclusions

Despite the reduction in bacterial meningitis incidence during the last decade, it remains a significant healthcare issue in Brazil. Meningococcal disease is responsible for the majority of the cases with group C the most common capsular type. Our study demonstrates the appropriateness of introduction of meningococcal vaccination in Brazil. Furthermore, this study provides a baseline for future evaluation of the impact of the vaccines introduction in Brazil and changes in disease epidemiology.     

Deconvolution of intergenic polymorphisms determining high expression of Factor H binding protein in meningococcus and their association with invasive disease

Neisseria meningitidis is a strictly human pathogen and is the major cause of septicemia and meningitis worldwide. Factor H binding protein (fHbp) is a meningococcal surface-exposed lipoprotein that binds the human Complement factor H allowing the bacterium to evade the host innate immune response. FHbp is also a key antigen in two vaccines against N. meningitidis serogroup B. Although the fHbp gene is present in most circulating meningococcal strains, level of fHbp expression varies among isolates and has been correlated to differences in promoter sequences upstream of the gene. Here we elucidated the sequence determinants that control fHbp expression in globally circulating strains. We analyzed the upstream fHbp intergenic region (fIR) of more than 5800 strains representative of the UK circulating isolates and we identified eleven fIR sequence alleles which represent 88% of meningococcal strains. By engineering isogenic recombinant strains where fHbp expression was under the control of each of the eleven fIR alleles, we confirmed that the fIR sequence determines a specific and distinct level of expression. Moreover, we identified the molecular basis for variation in expression through polymorphisms within key regulatory regions that are known to affect fHbp expression. We experimentally established three expression groups, high–medium–low, that correlated directly with the susceptibility to killing mediated by anti-fHbp antibodies and the ability of the meningococcal strain to survive within human serum. By using this sequence classification and information about the variant, we predicted fHbp expression in the panel of UK strains and we observed that strains with higher expressing fIR alleles are more likely associated with invasive disease. Overall, our findings can contribute to understand and predict vaccine coverage mediated by fHbp as well as to shed light on the role of this virulence factor in determining an invasive phenotype.     

Analysis of outer membrane porin complexes of Neisseria meningitidis in wild‐type and specific knock‐out mutant strains

The structure of the porin complexes of Neisseria meningitidis was assessed in the vaccine strain H44/76 and its homologous mutants lacking the main porins (PorA and PorB) and other outer membrane (OM) components (RmpM and FetA). The analysis using 1‐D blue native (BN) electrophoresis, 2‐D BN/SDS‐PAGE and 2‐D diagonal electrophoresis, followed by LC/MS‐MS (for 1‐D gels) or MALDI‐TOF (for 2‐D gels) revealed at least six porin complexes in the wild‐type strain with molecular masses (MW) ranging from 145 to 195 kDa and variable composition: The two higher MW complexes are formed by PorA, PorB and RmpM, the following three are formed by PorA and PorB, and the lower MW one is formed by only PorB. Complexes in the mutants lacking either PorA, PorB or RmpM, but not those in the mutant lacking FetA, were alterered respect to those in the wild‐type strain. The most evident alteration was seen in the mutant lacking PorB, in which PorA formed only a high MW complex (≈?800 kDa). Our results suggest that PorA and PorB could form a ‘basic’ template for the transportation systems in the OM of the meningococci. Other proteins (such as RmpM) could be transiently associated to the porin complexes, depending on the specific tranport needs at different stages of the meningococcal life cycle, resulting in a dynamic net of pores of variable composition.     

Streptococcus pneumoniae recruits complement factor H through the amino terminus of CbpA

Streptococcus pneumoniae, a human pathogen, is naturally capable of colonizing the upper airway and sometimes disseminating to remote tissue sites. Previous studies have shown that S. pneumoniae is able to evade complement-mediated innate immunity by recruiting complement factor H (FH), a complement alternative pathway inhibitor. Pneumococcal binding to FH has been attributed to choline-binding protein A (CbpA) of S. pneumoniae and its allelic variants, all of which are surface-exposed proteins. In this study, we sought to determine the molecular basis of the CbpA-FH binding interaction. Initial deletional analysis of the CbpA protein in strain D39 (capsular serotype 2) revealed that the N-terminal region of 89 amino acids in the mature CbpA protein is required for FH binding. Immunofluorescence microscopy analysis showed that this region of CbpA is also necessary for FH deposition to the surface of the intact pneumococci. Moreover, recombinant proteins representing the 104 amino acids of the N-terminal CbpA alone was sufficient for high affinity binding to FH (KD < 1 nm). The FH binding activity was finally localized to a 12-amino acid motif in the N-terminal CbpA by peptide mapping. Further kinetic analysis suggested that additional amino acids downstream of the 12-amino acid motif provide necessary structural or conformational support for the CbpA-FH interaction. The 12-amino acid motif and its adjacent regions contain highly conserved residues among various CbpA alleles, suggesting that this region may mediate FH binding in multiple pneumococcal strains.     

Interaction of Human Laminin Receptor with Sup35, the [PSI +] Prion-Forming Protein from S. cerevisiae: A Yeast Model for Studies of LamR Interactions with Amyloidogenic Proteins

The laminin receptor (LamR) is a cell surface receptor for extracellular matrix laminin, whereas the same protein within the cell interacts with ribosomes, nuclear proteins and cytoskeletal fibers. LamR has been shown to be a receptor for several bacteria and viruses. Furthermore, LamR interacts with both cellular and infectious forms of the prion protein, PrP^C and PrP^Sc. Indeed, LamR is a receptor for PrP^C. Whether LamR interacts with PrP^Sc exclusively in a capacity of the PrP receptor, or LamR specifically recognizes prion determinants of PrP^Sc, is unclear. In order to explore whether LamR has a propensity to interact with prions and amyloids, we examined LamR interaction with the yeast prion-forming protein, Sup35. Sup35 is a translation termination factor with no homology or functional relationship to PrP. Plasmids expressing LamR or LamR fused with the green fluorescent protein (GFP) were transformed into yeast strain variants differing by the presence or absence of the prion conformation of Sup35, respectively [PSI ⁺] and [psi ⁻]. Analyses by immunoprecipitation, centrifugal fractionation and fluorescent microscopy reveal interaction between LamR and Sup35 in [PSI ⁺] strains. The presence of [PSI ⁺] promotes LamR co-precipitation with Sup35 as well as LamR aggregation. In [PSI ⁺] cells, LamR tagged with GFP or mCherry forms bright fluorescent aggregates that co-localize with visible [PSI ⁺] foci. The yeast prion model will facilitate studying the interaction of LamR with amyloidogenic prions in a safe and easily manipulated system that may lead to a better understanding and treatment of amyloid diseases.     

Incorporation of Real-Time PCR into Routine Public Health Surveillance of Culture Negative Bacterial Meningitis in S?o Paulo,Brazil

Real-time (RT)-PCR increases diagnostic yield for bacterial meningitis and is ideal for incorporation into routine surveillance in a developing country. We validated a multiplex RT-PCR assay for Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae in Brazil. Risk factors for being culture-negative, RT-PCR positive were determined. The sensitivity of RT-PCR in cerebrospinal fluid (CSF) was 100% (95% confidence limits, 96.0%–100%) for N. meningitidis, 97.8% (85.5%–99.9%) for S. pneumoniae, and 66.7% (9.4%–99.2%) for H. influenzae. Specificity ranged from 98.9% to 100%. Addition of RT-PCR to routine microbiologic methods increased the yield for detection of S. pneumoniae, N. meningitidis, and H. influenzae cases by 52%, 85%, and 20%, respectively. The main risk factor for being culture negative and RT-PCR positive was presence of antibiotic in CSF (odds ratio 12.2, 95% CI 5.9-25.0). RT-PCR using CSF was highly sensitive and specific and substantially added to measures of meningitis disease burden when incorporated into routine public health surveillance in Brazil.     

Association of secondhand smoke exposure with pediatric invasive bacterial disease and bacterial carriage: a systematic review and meta-analysis

Background

A number of epidemiologic studies have observed an association between secondhand smoke (SHS) exposure and pediatric invasive bacterial disease (IBD) but the evidence has not been systematically reviewed. We carried out a systematic review and meta-analysis of SHS exposure and two outcomes, IBD and pharyngeal carriage of bacteria, for Neisseria meningitidis (N. meningitidis), Haemophilus influenzae type B (Hib), and Streptococcus pneumoniae (S. pneumoniae).

Methods and Findings

Two independent reviewers searched Medline, EMBASE, and selected other databases, and screened articles for inclusion and exclusion criteria. We identified 30 case-control studies on SHS and IBD, and 12 cross-sectional studies on SHS and bacterial carriage. Weighted summary odd ratios (ORs) were calculated for each outcome and for studies with specific design and quality characteristics. Tests for heterogeneity and publication bias were performed. Compared with those unexposed to SHS, summary OR for SHS exposure was 2.02 (95% confidence interval [CI] 1.52–2.69) for invasive meningococcal disease, 1.21 (95% CI 0.69–2.14) for invasive pneumococcal disease, and 1.22 (95% CI 0.93–1.62) for invasive Hib disease. For pharyngeal carriage, summary OR was 1.68 (95% CI, 1.19–2.36) for N. meningitidis, 1.66 (95% CI 1.33–2.07) for S. pneumoniae, and 0.96 (95% CI 0.48–1.95) for Hib. The association between SHS exposure and invasive meningococcal and Hib diseases was consistent regardless of outcome definitions, age groups, study designs, and publication year. The effect estimates were larger in studies among children younger than 6 years of age for all three IBDs, and in studies with the more rigorous laboratory-confirmed diagnosis for invasive meningococcal disease (summary OR 3.24; 95% CI 1.72–6.13).

Conclusions

When considered together with evidence from direct smoking and biological mechanisms, our systematic review and meta-analysis indicates that SHS exposure may be associated with invasive meningococcal disease. The epidemiologic evidence is currently insufficient to show an association between SHS and invasive Hib disease or pneumococcal disease. Because the burden of IBD is highest in developing countries where SHS is increasing, there is a need for high-quality studies to confirm these results, and for interventions to reduce exposure of children to SHS. Please see later in the article for the Editors'' Summary     

Bulged residues promote the progression of a loop-loop interaction to a stable and inhibitory antisense-target RNA complex

In several groups of bacterial plasmids, antisense RNAs regulate copy number through inhibition of replication initiator protein synthesis. These RNAs are characterized by a long hairpin structure interrupted by several unpaired residues or bulged loops. In plasmid R1, the inhibitory complex between the antisense RNA (CopA) and its target mRNA (CopT) is characterized by a four-way junction structure and a side-by-side helical alignment. This topology facilitates the formation of a stabilizer intermolecular helix between distal regions of both RNAs, essential for in vivo control. The bulged residues in CopA/CopT were shown to be required for high in vitro binding rate and in vivo activity. This study addresses the question of why removal of bulged nucleotides blocks stable complex formation. Structure mapping, modification interference, and molecular modeling of bulged-less mutant CopA–CopT complexes suggests that, subsequent to loop–loop contact, helix propagation is prevented. Instead, a fully base paired loop–loop interaction is formed, inducing a continuous stacking of three helices. Consequently, the stabilizer helix cannot be formed, and stable complex formation is blocked. In contrast to the four-way junction topology, the loop–loop interaction alone failed to prevent ribosome binding at its loading site and, thus, inhibition of RepA translation was alleviated.     

The Meningococcal Vaccine Candidate Neisserial Surface Protein A (NspA) Binds to Factor H and Enhances Meningococcal Resistance to Complement

Complement forms an important arm of innate immunity against invasive meningococcal infections. Binding of the alternative complement pathway inhibitor factor H (fH) to fH-binding protein (fHbp) is one mechanism meningococci employ to limit complement activation on the bacterial surface. fHbp is a leading vaccine candidate against group B Neisseria meningitidis. Novel mechanisms that meningococci employ to bind fH could undermine the efficacy of fHbp-based vaccines. We observed that fHbp deletion mutants of some meningococcal strains showed residual fH binding suggesting the presence of a second receptor for fH. Ligand overlay immunoblotting using membrane fractions from one such strain showed that fH bound to a ∼17 kD protein, identified by MALDI-TOF analysis as Neisserial surface protein A (NspA), a meningococcal vaccine candidate whose function has not been defined. Deleting nspA, in the background of fHbp deletion mutants, abrogated fH binding and mAbs against NspA blocked fH binding, confirming NspA as a fH binding molecule on intact bacteria. NspA expression levels vary among strains and expression correlated with the level of fH binding; over-expressing NspA enhanced fH binding to bacteria. Progressive truncation of the heptose (Hep) I chain of lipooligosaccharide (LOS), or sialylation of lacto-N-neotetraose LOS both increased fH binding to NspA-expressing meningococci, while expression of capsule reduced fH binding to the strains tested. Similar to fHbp, binding of NspA to fH was human-specific and occurred through fH domains 6–7. Consistent with its ability to bind fH, deleting NspA increased C3 deposition and resulted in increased complement-dependent killing. Collectively, these data identify a key complement evasion mechanism with important implications for ongoing efforts to develop meningococcal vaccines that employ fHbp as one of its components.     

Crystallographic analysis of Neisseria meningitidis PorB extracellular loops potentially implicated in TLR2 recognition

Among all Neisseriae species, Neisseria meningitidis and Neisseria gonorrhoeae are the only human pathogens, causative agents of bacterial meningitis and gonorrhoea, respectively. PorB, a pan-Neisseriae trimeric porin that mediates diffusive transport of essential molecules across the bacterial outer membrane, is also known to activate host innate immunity via Toll-like receptor 2 (TLR2)-mediated signaling. The molecular mechanism of PorB binding to TLR2 is not known, but it has been hypothesized that electrostatic interactions contribute to ligand/receptor binding. Strain-specific sequence variability in the surface-exposed loops of PorB which are potentially implicated in TLR2 binding, may explain the difference in TLR2-mediated cell activation in vitro by PorB homologs from the commensal Neisseriae lactamica and the pathogen N. meningitidis. Here, we report a comparative structural analysis of PorB from N. meningitidis serogroup B strain 8765 (63% sequence homology with PorB from N. meningitidis serogroup W135) and a mutant in which amino acid substitutions in the extracellular loop 7 lead to significantly reduced TLR2-dependent activity in vitro. We observe that this mutation both alters the loop conformation and causes dramatic changes of electrostatic surface charge, both of which may affect TLR2 recognition and signaling.     

Identification of antisense RNA stem–loops that inhibit RNA–protein interactions using a bacterial reporter system

Many well-characterized examples of antisense RNAs from prokaryotic systems involve hybridization of the looped regions of stem–loop RNAs, presumably due to the high thermodynamic stability of the resulting loop–loop and loop–linear interactions. In this study, the identification of RNA stem–loops that inhibit U1A protein binding to the hpII RNA through RNA–RNA interactions was attempted using a bacterial reporter system based on phage λ N-mediated antitermination. As a result, loop sequences possessing 7–8 base complementarity to the 5′ region of the boxA element important for functional antitermination complex formation, but not the U1 hpII loop, were identified. In vitro and in vivo mutational analysis strongly suggested that the selected loop sequences were binding to the boxA region, and that the structure of the antisense stem–loop was important for optimal inhibitory activity. Next, in an attempt to demonstrate the ability to inhibit the interaction between the U1A protein and the hpII RNA, the rational design of an RNA stem–loop that inhibits U1A-binding to a modified hpII was carried out. Moderate inhibitory activity was observed, showing that it is possible to design and select antisense RNA stem–loops that disrupt various types of RNA–protein interactions.     

Sequence Diversity, Predicted Two-Dimensional Protein Structure, and Epitope Mapping of Neisserial Opa Proteins

The sequence diversity of 45 Opa outer membrane proteins from Neisseria meningitidis, Neisseria gonorrhoeae, Neisseria sicca, and Neisseria flava indicates that horizontal genetic exchange of opa alleles has been rare between these species. A two-dimensional structural model containing four surface-exposed loops was constructed based on rules derived from porin crystal structure and on conservation of sequence homology within transmembrane β-strands. The minimal continuous epitopes recognized by 23 monoclonal antibodies were mapped to loops 2 and 3. Some of these epitopes are localized on the bacterial cell surface, in support of the model.     

Class 1 outer membrane protein of Neisseria meningitidis: epitope analysis of the antigenic diversity between strains, implications for subtype definition and molecular epidemiology

The VR1 and VR2 regions of the class 1 protein have been sequenced from a number of meningococcal strains, including non-subtypable strains and strains of apparently identical subtype. The amino acid sequences have been used to construct synthetic peptides for mapping subtype-specific epitopes. The majority of epitopes was found to be located in VR2 at the apex of a predicted surface-exposed loop. A single amino acid change within an epitope, or an amino acid deletion outside an epitope, were both associated with loss of subtype specificity, resulting from a change in the predicted conformation at the apex of the loop structure. Analysis of the sequence information combined with knowledge of defined epitopes also revealed considerable additional information not demonstrated by current subtyping procedures.     

Outer membrane protein P1 is the CEACAM‐binding adhesin of Haemophilus influenzae

Haemophilus influenzae is a Gram‐negative pathogen colonizing the upper respiratory tract mucosa. H. influenzae is one of several human‐restricted bacteria, which bind to carcinoembryonic antigen‐related cell adhesion molecules (CEACAMs) on the epithelium leading to bacterial uptake by the eukaryotic cells. Adhesion to CEACAMs is thought to be mediated by the H. influenzae outer membrane protein (OMP) P5. However, CEACAMs still bound to H. influenzae lacking OMP P5 expression, and soluble CEACAM receptor ectodomains failed to bind to OMP P5, when heterologously expressed in Escherichia coli. Screening of a panel of H. influenzae OMP mutants revealed that lack of OMP P1 completely abrogated CEACAM binding and supressed CEACAM‐mediated engulfment of H. influenzae by epithelial cells. Moreover, ectopic expression of OMP P1 in E. coli was sufficient to induce CEACAM binding and to promote attachment to and internalization into CEACAM‐expressing cells. Interestingly, OMP P1 selectively recognizes human CEACAMs, but not homologs from other mammals and this binding preference is preserved upon expression in E. coli. Together, our data identify OMP P1 as the bona fide CEACAM‐binding invasin of H. influenzae. This is the first report providing evidence for an involvement of the major OMP P1 of H. influenzae in pathogenesis.     

Loop residues of the receptor binding domain of Bacillus thuringiensis Cry11Ba toxin are important for mosquitocidal activity

Using a Cry11Ba toxin model, predicted loops in domain II were analyzed for their role in receptor binding and toxicity. Peptides corresponding to loops α8, 1 and 3, but not loop 2, competed with toxin binding to Aedes midgut membranes. Mutagenesis data reveal loops α8, 1 and 3 are involved in toxicity. Loops 1 and 3 are of greater significance in toxicity to Aedes and Culex larvae than to Anopheles. Cry11Ba binds the apical membrane of larval caecae and posterior midgut, and binding can be competed by loop 1 but not by loop 2 peptides. Cry11Ba binds the same regions to which anti-cadherin antibody binds, and this antibody competes with Cry11Ba binding suggesting a possible role of cadherin in toxication.     

Associations between Pathogens in the Upper Respiratory Tract of Young Children: Interplay between Viruses and Bacteria

Background

High rates of potentially pathogenic bacteria and respiratory viruses can be detected in the upper respiratory tract of healthy children. Investigating presence of and associations between these pathogens in healthy individuals is still a rather unexplored field of research, but may have implications for interpreting findings during disease.

Methodology/Principal Findings

We selected 986 nasopharyngeal samples from 433 6- to 24-month-old healthy children that had participated in a randomized controlled trial. We determined the presence of 20 common respiratory viruses using real-time PCR. Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis and Staphylococcus aureus were identified by conventional culture methods. Information on risk factors was obtained by questionnaires. We performed multivariate logistic regression analyses followed by partial correlation analysis to identify the overall pattern of associations. S. pneumoniae colonization was positively associated with the presence of H. influenzae (adjusted odds ratio 1.60, 95% confidence interval 1.18–2.16), M. catarrhalis (1.78, 1.29–2.47), human rhinoviruses (1.63, 1.19–2.22) and enteroviruses (1.97, 1.26–3.10), and negatively associated with S. aureus presence (0.59, 0.35–0.98). H. influenzae was positively associated with human rhinoviruses (1.63, 1.22–2.18) and respiratory syncytial viruses (2.78, 1.06–7.28). M. catarrhalis colonization was positively associated with coronaviruses (1.99, 1.01–3.93) and adenoviruses (3.69, 1.29–10.56), and negatively with S. aureus carriage (0.42, 0.25–0.69). We observed a strong positive association between S. aureus and influenza viruses (4.87, 1.59–14.89). In addition, human rhinoviruses and enteroviruses were positively correlated (2.40, 1.66–3.47), as were enteroviruses and human bocavirus, WU polyomavirus, parainfluenza viruses, and human parechovirus. A negative association was observed between human rhinoviruses and coronaviruses.

Conclusions/Significance

Our data revealed high viral and bacterial prevalence rates and distinct bacterial-bacterial, viral-bacterial and viral-viral associations in healthy children, hinting towards the complexity and potential dynamics of microbial communities in the upper respiratory tract. This warrants careful consideration when associating microbial presence with specific respiratory diseases.     

The Association of Meningococcal Disease with Influenza in the United States, 1989–2009

Importance and Objective

Prior influenza infection is a risk factor for invasive meningococcal disease. Quantifying the fraction of meningococcal disease attributable to influenza could improve understanding of viral-bacterial interaction and indicate additional health benefits to influenza immunization.

Design, Setting and Participants

A time series analysis of the association of influenza and meningococcal disease using hospitalizations in 9 states from 1989–2009 included in the State Inpatient Databases from the Agency for Healthcare Research and Quality and the proportion of positive influenza tests by subtype reported to the Centers for Disease Control. The model accounts for the autocorrelation of meningococcal disease and influenza between weeks, temporal trends, co-circulating respiratory syncytial virus, and seasonality. The influenza-subtype-attributable fraction was estimated using the model coefficients. We analyzed the synchrony of seasonal peaks in hospitalizations for influenza, respiratory syncytial virus, and meningococcal disease.

Results and Conclusions

In 19 of 20 seasons, influenza peaked≤2 weeks before meningococcal disease, and peaks were highly correlated in time (ρ = 0.95; P <.001). H3N2 and H1N1 peaks were highly synchronized with meningococcal disease while pandemic H1N1, B, and respiratory syncytial virus were not. Over 20 years, 12.8% (95% CI, 9.1–15.0) of meningococcal disease can be attributable to influenza in the preceding weeks with H3N2 accounting for 5.2% (95% CI, 3.0–6.5), H1N1 4.3% (95% CI, 2.6–5.6), B 3.0% (95% CI, 0.8–4.9) and pH1N1 0.2% (95% CI, 0–0.4). During the height of influenza season, weekly attributable fractions reach 59%. While vaccination against meningococcal disease is the most important prevention strategy, influenza vaccination could provide further protection, particularly in young children where the meningococcal disease vaccine is not recommended or protective against the most common serogroup.